As is well known to those skilled in the art, cable ties, or straps are used to bundle or secure a group of articles such as electrical wires and cables. Cable ties of conventional construction include a cable tie head and an elongated tail extending therefrom. The tail is wrapped around a bundle of articles and thereafter inserted through a passage in the head. The head of the cable tie typically supports a locking element which extends into the head passage and engages the body of the tail to secure the tail to the head.
In practice, the installer manually places the tie about the articles to be bundled, inserts the tail through the head passage and then manually tightens the tie about the bundle. At this point, a cable tie installation tool is used to tension the cable tie to a predetermined tension. One or more grip strokes may be needed to sufficiently tension the tie depending upon how tightly the installer manually tensions such tie. Once the strap tension approaches the desired predetermined tension setting level, the tool severs the excess tail portion from the tie, i.e., that portion of the tail which extends beyond the head of the cable tie.
The tools of the prior art, although capable of tensioning and thereafter severing the excess tail portion of the cable tie, typically have several disadvantages associated therewith which, either singularly or plurally, increase operator injuries due to poor ergonomics, or result in tool failure or degradation of reliability such that consistent proper installation of a cable tie becomes impossible. For example, the cast metal body tool disclosed in U.S. Pat. No. 3,661,187 to Caveney et al., uses a conventional linkage style tensioning and severing assembly. The design of this tool housing is not very ergonomic, but operatively, the linkage design is extremely durable. The cast metal body provides apertures in which pins or shafts are secured to mount and provide pivot points for the many linkage arms. Since the linkage style of tensioning and severing assembly generates such high forces at the pin locations and cantilevered loads, the durable cast metal body becomes a necessity for reliable operation and to keep the pins from distorting the housing and migrating. Using the stored energy principle of a partially compressed spring, accurate and predictable severance breakaway is achieved when the pins cannot move and the arms move through their indented movements. However, a disadvantage of the cast metal body is that it requires a significant number of manufacturing steps, driving the cost higher.
Other prior art examples include U.S. Pat. Nos. 4,793,385, 4,997,011, and 5,492,156, all to Dyer et al., which disclose a plastic bodied tool having improved ergonomics. A conventional linkage style arrangement similar to that disclosed in Caveney et al., is used, but the tension adjustment assembly has been moved to the top of the tool. In this location, the operator can easily see and manipulate the tension adjustment knobs. Additionally, a more deeply curved handle is shown, however, in practice the foam handle cover used therewith yields a final result which is not a very ergonomic. The major disadvantage of this tool is the incorporation of the high angular force linkage design, known previously, with the plastic body. As a result of this combination, the tool is not nearly as durable as previous designs. The high off-center loading forces of the linkage design are exerted on the pins mounted in the plastic body. As the number of use repetitions of the tool increase, the pin holes become elongated and allow the pins to migrate or wobble. Consequently, the clear breakaway point which commonly distinguishes the linkage style design becomes unpredictable and correct tensioning is not possible. Not only does this give the tool operator a vague sense of the proper tension, but inaccurate and inconsistent tensioning of the cable tie strap is also a result. Ultimately, this tool will fail to produce any reasonably repeatable results, after which the tool must be discarded as unusable.
The most recent prior art tool described in U.S. Pat. No. 5,915,425 to Nilsson et al., proposes to solve several ergonomic disadvantages of prior tools, namely, adjustable grip size, rotatable nose, and reduced recoil shock/vibration. While attempting to overcome these disadvantages, the plastic bodied tool incorporated a variation on tensioning and severing assemblies previously disclosed. However, this design in practice has resulted in a poorly performing tool that is not durable, subject to tensioning inaccuracies between tools, fails to provide a clear breakaway on cutoff, has the inability to accurately calibrate the tension settings, and uses a fragile tension setting device.
There is therefore a need in the art for an installation tool which is ergonomic, reliable, durable, provides a consistent cutoff height, comprises a lightweight plastic housing, and provides a clear cutoff breakaway point.